Haematococcus is a microalga that is capable of producing astaxanthin, a high value carotenoid with antioxidant properties. The culturing process from beginning to end is relatively long compared to other common microalgae, such as Chlorella or Nannochloropsis, and results in a number of challenges to the survival of Haematococcus cells due to the nature of Haematococcus as a slow growing microalga. Over the course of the culturing process, the Haematococcus cells must go through a growth and cell division phase to accumulate biomass before entering a second stage where growth and motility is halted but astaxanthin is accumulated in the cells before harvest. Operating this long multi-stage culturing process as an open culture increases exposure of the cells to the dangers of contamination, a sub-optimal environment, or other conditions which reduce the survival rate of the cells and ultimately the quantity and quality of the astaxanthin harvest.
Developing treatments for increasing the survival rate of Haematococcus cultures must take into account the sensitivities of the cells at the different stages, impact on biomass growth, and impact on astaxanthin production, as well as effectiveness of the treatment over the long culturing process. Treatments developed for faster growing microalgae or microalgae cultured for production of whole biomass, lipids, or proteins, such as treatment with oxidative agents or commercially available herbicides, fungicides, and pesticides, have not been shown to be easily translatable to Haematococcus cultures due to the unique stages of the Haematococcus culturing process, the sensitivities of Haematococcus cells, and the desire to use the targeted end product of Haematococcus cultures in human consumption product industries (e.g., nutritional supplements, food enhancers, therapeutic compositions). Therefore, there is a need in the art to development treatment methods for increasing the survival rate of Haematococcus cells before and during the astaxanthin accumulation stage, without adversely affecting the cells and value of the end product.